The present invention relates to golf-club and golf-ball testing apparatus, and more particularly to an apparatus for mechanically swinging a golf club for the purpose of testing the club or the ball.
The problems in testing golf clubs are significantly more involved than in testing golf balls. In the case of testing the latter, it would be sufficient to devise a mechanism for impacting a ball with a mallet using energy calculated to produce a predetermined initial velocity. To test golf clubs, however, it is desirable to control motion of the club from the top of the back swing to impact and beyond to follow through in a manner more nearly duplicating the motion that would be produced by a golfer.
Nearly every golfer has a different swing because of individual factors that vary from person to person, such as height, arm length, strength and the like. It would therefore not be practical to devise a mechanism for swinging a golf club that duplicates the swing of a particular person. However, it is important that a typical or average golfer be duplicated in order to truly test features of golf clubs, such as head or shaft design. Otherwise a tendency for the golf club to slice or hook the ball under normal golfing conditions may not be detected. In attempting to duplicate a normal swing of a golfer, it must be understood that the normal swing is not one which produces motion of the club head in a perfect circle like a spinning wheel, although it is helpful for golfers to visualize that swing pattern. Consequently, in devising a golf club swinging apparatus, it is not sufficient for the machine to swing the club about a fixed axis like a spoke in a wheel.
In visualizing the perfect swing to be like a spoked wheel spinning in a fixed plane at an acute angle with the ground, one fails to account for the fact that the center of the swing is not the center of the golfer's chest. It is instead more nearly at the leading shoulder of the golfer. The leading shoulder is that nearest the green, namely the left shoulder in the case of the right handed golfer. That center (shoulder point) is not fixed in space during the course of a normal swing, although the golfer strives to keep his head fixed in space, while virtually all of his body moves during the course of the swing. First it moves away from the target during the back swing. To raise the golf club up, back and around in the back swing, the leading shoulder dips below the center of the golfer's chest and moves closer to that center. Then during the down swing, the leading shoulder retraces its path and during the follow through rises above and closer to the center of the golfer's chest. All through the swing, the golfer not only pivots the golf club about his wrists but also rolls the club shaft such that, during the back swing, the club head moves further back away from a position normal to the direction of motion as the golfer cocks his wrists until, at the top of the back swing, the shaft has been rolled through about 90.degree.. During the down swing, the shaft is rolled back as the wrists are uncocked. During the follow through the golfer continues to roll the club shaft through another 90.degree., more or less, as he cocks his wrists to break the swing.
If the golfer is consistent in his swing, he can quickly determine for himself how he should address the ball in order for the club head to be seemingly square at the moment of impact. For example, if there is a tendency to slice, the club head is apparently open (rotated back) at the moment of impact. The golfer compensates by addressing the ball with the club head initially closed. to be able to accomplish the same thing with precision for testing a golf club design, i.e., to be able to open or close the club head to a desired fine degree in addressing the ball, it would be desirable to not only be able to duplicate the rolling motion of the golfer's wrists but to also be able to initially open or close the club head before starting the down swing, usually while addressing the ball before starting the back swing.